Process for the production of paper pulp and the like



'new and useful Patented Apr. ld, i923.

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No Drawing.

To all 'whom t muy conc-eraf y Y 'Be it lrnoiviipthat l5 lniriimsii S tzuiu'iins, a citizen ofthevllnitedritates, residing at Port Huron, county' ,of Saint Clair, andL What 'islinoivn as bisuliit-e oicalciuni, though i the material may contain ymore or less niegnesium or indeed other bi-sultites may be employed. `While this'material iscominonly known as bisulte, it does not strictly con Aform to formula and Where l have used the termy l Wish it to be understood as signifying an acid salt oi sulfurous acid or a sullite dissolved in sulfurous acid. pose of my invention the bi-sulte may be made up in any usual or approved manner and used in the usual proportions to'` the material to be treated, though my invention is not limited thereto.

. My invention is based upon the discovery that if a proper amount oi a reducing agent is introduced into the-cooking acid `(the bisuliite solution) considerably enhanced ryields of pulp are obtained and the product is of a better quality. l `have found that the best results are obtained by introducing into the cooking acid a relatively small amount ot liydrio-sultiirous acid.` Hydrosulfurous acid is a powerful reducing agent, which. under proper conditions is converted y oxidation intosuliurous acid, Without undue precipitation of sulfur. lNhen this material is added to or produced in the liquor in whichv the pulp is digested the lsource of hydro-sulurousproper reducing conditions occur' to produce the increased and improved yield referred to above. lt is to be uiiderstood vthat Where I .use the term hydro-sulicurous acid hereinutter l include therein salts 'of the acid and i also materials whiclrare capable of producing the acid when addedto the digesting liquor. I may mention as suiiable acid,- `sodium bydro-suliite, Which is an article of vcom- For the pur-v vinto the digester.

appiieauon inea agili ai. i922. semina. 555-,e9s I y l merce Aand may be obtainedupontlie-maryiret.- TWhen an `acid .such as sulfurous 'acid is .added to vthis salt'dfr'ee hydro-suliurous acid is iormed.4 -Thus when the salt is-added tothe cook in the process of` digesting Wood the Asulturousv acid inthe liquor reacts with the .salt producing hydro-sullurous acid-and sodium suliite, according to the equation Na2s2o+i-i,so3demandada The liydro-sulturous acid gradually `c"oinbinesivith the calcium sulicite present during the progress ofthedigestionv` the yreaction being somewhat 'obscure buty in fall probability, ai calciumhydro-suliiteiis formed cording to the equation y Heston'oasoieoaaoartsoi. il The presence .of the `calcium sulfite in the cooking liquor seems to have a pronounced influence in preserving the hydro-sulfurous acid from decomposition, except in the inanner above noted, and the hydro-sulfurous y acid in so-ine manner affects the action of the calcium sultite to increasel vthe yield and quality of the pulp, apparently by preventing the liquor from attacking the cellulose.

While my process may be performedas above described, by the addition of sodium hydro-sulte to the liquor, I preferto form the hydro-sulfurous acid in the-liquor by the addition oi' a suitable metal such as zinc or magnesium. lVVhenZinc is dissolved in sulfurous acid hydro-sulfurous acid is generated according to the following equation Therefore when zinc or other suitable metal is added to the cook in the suliite process it reacts With the sulfurous acid present, forining hydro-sulfurous acid. Preferablyr the zinc isadded in the form of a powder and it is convenient to sprinkle it on the chipsas.

they are charged into the digester. It `some ymetal other than zinc is used the proper.

quantity may be determined` fromthe ratio of its atomic Weight to that of Zinc. As sof l dium hydro-sultite is very soluble it may be added to the acid before it is introduced lent o't'a pound of the sodium hydro-sulfite. The quantity of sodium,hydro-suliite,y or powdered Zinc to be used Varies considerably in accordancejwith the result desired. Ordinarily ten to twenty lpounds"thereof For practical purposes. a pound of'zinc may be takenr as theequiva-l iio may be used in a l0 ton digester holding about 22,000 gallons of liquor and about tons of chips, the strength of the acid being about 4` per cent, of which .approximatelyv 2.60 per cent is free acid and 1.40 per cent combined. lVith such a charge I have found twelve pounds ,of Zinc dus-t to be a very satisfactory addition. It the metal or sodium hydro-suliite addition is increased beyond the proportions mentioned the pulp begins to get too tough to Work Well in the machinery utilized in reducing it, though for certain purposes Where a tougher pulp is required the proportions of zinc or sodium hydro-sulte may be somewhat greater than i that mentioned.

From the above it Will be evident that my process may be practical Without altering lthe conditions of paper pulp manufacture or the apparatus used except by the addition of the material for furnishing hydro-sulfurous acid and this is true as Well of the so-called quick-cook or'Rfitter-Kelner process as of the Mitschcrlich or slow-cook process.

I claim:

k1.' A process of producing vsuhite Wood pulp, Which consists in cooking the wood in a solution containing a bi-sulte and hydrosulfurous acid.

2. A process of producing sulfite Wood pulp, which consists in cooking the Wood in a solution containing a bi-sulte and a material capable of producing hydro-sulfurous acid.

3. A process of producing sulfite Wood pulp, consisting in cooking the Wood in a solution of bi-sulite containing a metal capable of producing with the bi-sulfite hydroesulfurous acid.

4. A process for producing sulfite Wood pulp, which consists in cooking the wood in a solution containing bi-sulite and a compound of hydro-sulfurous acid.

5. A process of preparing sulfite Wood pulp, which consists in cooking the Wood in a solution containing bi-sulte in the presence of zinc.

6. The herein described process of preparing vegetable fibres consisting in cooking the same in a solution containing a bi-sullitc and hydro-sulfurous acid.

BERTRAND S. SUMMERS. 

